Recent but limited epidemiologic data suggest that the current national ambient standard for particle matter may not be adequate to protect public health and that particle acidic sulfate aerosol may be associated with adverse respiratory effects. An Ambient Air Quality Standard for acidic aerosol is being considered. we will examine these two air pollutants, which are of major interest to outdoor air quality, in an indoor environment where multiple and potentially interacting exposures to complex mixtures can be quantified with more reliability than is done in outdoor studies. We have identified unvented kerosene space heaters as a major source of residential particle mass, sulfate and vapor and particle acid. A pilot study has indicated that kerosene heater users are at higher risk for respiratory symptoms and as such constitute a unique population in which to determine the nature of an association between particle mass, sulfate mass and vapor and particle acid exposures and respiratory health effects. This study tests the hypothesis that exposures to elevated concentrations of particle mass (including fine particle mass), and acidic sulfate aerosol air contaminants, resulting from kerosene heater use are associated with an increased risk of acute or chronic upper and lower respiratory symptoms in infants age 3-15 months (a sensitive population), including cough, phlegm, wheeze, runny/stuffy nose, etc. Also tested is the hypothesis that the exposed mothers of the infants are at an increased risk of respiratory symptoms and reversible decrements in peak expiratory flow. These associations will be evaluated for an exposure response relation while adjusting for other known or potential risk factors (NO., HN02, SES, health status, etc.). The study population, selected from live deliveries occurring at four Connecticut hospitals, will exclude homes where passive smoking exposure occurs. Study subjects will be recruited into three exposure categories: a) no unvented combustion sources (N=450 infants and their mothers); b) gas ranges only (N=225 infants and their mothers); and, c) kerosene heaters only (N=225 infants and their mothers). Data will be gathered for one year on a bi-weekly basis, covering a full heating and cooling season, including reports of respiratory symptoms in both the infants and mothers and concurrent use of the heater and gas stove. Diurnal peak flow differences for the mothers for a 4 week period during the heating and non-heating seasons will be recorded. A nested exposure assessment protocol will be used and potential confounding factors will be controlled. Continuous versus categorical responses in the exposure groups will be compared using longitudinal analysis. This design will allow for a distinction between exposure effects and seasonal variation effects. The results would provide data needed to address the recently raised public health issues of whether the particle ambient standard protects public health and whether a national ambient acid standard is needed. It will also identify any increased risk for the large population of kerosene heater users.